4.1 - 18
MTP700 Portable Radio / Detailed Service Manual
TRANSCEIVER 400 MHz
Transmit PLL
The TX VCO is a discrete VCO that is controlled by the ESCORT IC U7001. The VCO
produces the TX frequency signals in the frequency band 380-430MHz. A discrete coil
L7501 is used in the tank circuit of the VCO. Four tuning diodes (D7501-D7504) and the
variable feedback by D7505 ensure excellent performance in noise behaviour and signal
level stability throughout the whole band. A cascode amplifier is used as buffer to mini-
mize the impact of load pull on the VCO frequency.
The synthesizer IC is the ESCORT IC U7001 employing NUD (near-unity-divider) tech-
nique to provide fast lock-in to TX frequency using a high reference frequency. The Main
synthesizer is used as reference frequency source. The signal frequency of the Main
VCO is divided by 41/32 and compared with the TX VCO frequency in the fast phase
comparator of the ESCORT. The comparator output signals IUP and IDOWN then control
the current mirrors Q7021 and Q7022 to supply the tuning voltage to low pass filter
C7011, C7012, R7011 and voltage range extension transistors Q7023 and Q7024 to the
tuning diodes. The ESCORT is controlled by the RedCap2 via SPIA_CLK; SPIA_MOSI
and SPIA_CS1_ESCORT.
Digital & Audio Section, Detailed Circuit Description
See Figure 4.1-9.
Figure 4.1-9 Digital Section - Detailed Circuit Diagram
JTAG
SOFT_TURN_OFF
SPIB
Reset
USB/RS232
CE_ON_OFF
INT_MIC
Headset/Keyfail
SIDE_OPT_SEL3
(from 24-pin connector)
SIDE_OPT_SEL1
(from 24-pin connector)
SIDE_OPT_SEL2
(from 24-pin connector)
REDCAP2
Audio
PA
16-pin
Connector
GCAP3
24-pin
Connector
40-pin
Connector
REDCAP2
TXE
RF Section
TETRA
BBP
SPIA
Display
Keypad
OPT SEL
Buffer
INT_SPKR
EXT_SPKR
INT_EAR
Vibrator
Side Data
EXT_MIC
S
On/Off
Vol knob
REDCAP2
FLASH 4M x 16 bit
SRAM 512k x 16 bit
Содержание IMPRES Tetra MTP700
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